COPD (chronic obstructive pulmonary disease) is a long-lasting lung disease usually caused by long-term smoking. COPD can get worse, making people sick enough to need hospitalization. Corticosteroids are very effective and are almost always used, but nobody knows the right dose. High doses may work better but could cause more side effects than low doses. Typical treatment lengths last at least one week. This study will be comparing two common regimens: either 40mg of corticosteroids daily (low dose), or 80mg of corticosteroids daily (high dose). It is unknown which regimen works better..